Down's Syndrome

What is Down's Syndrome?

People with Down's syndrome (sometimes called trisomy 21) have an extra chromosome, having three copies of chromosome 21 instead of 2. Chromosomes carry genes which pass certain characteristics from parents to their children. Abnormalities can occur when there are too many chromosomes.

Children with Down's syndrome will have a learning disability and may have other abnormalities such as heart defects. Older mothers are more likely to have a baby with Down's syndrome. For example, Down's syndrome occurs once in every 1500 births to women aged 20 years whereas at 40 the rate is increased to 1 in 100 births.

Can a scan detect Down's Syndrome?

Ultrasound scans can detect some problems which may suggest the baby has an increased risk ot having Down's syndrome but most babies with this condition appear normal at the 20 week scan. Unfortunately there is no way of predicting the degree of disability from an ultrasound of the baby. However a scan can pick up structural problems in a baby, for example, a problem with the heart. If however the baby has no apparent structural markers then one way to detect Down's syndrome is by amniocentesis.

Are there any other tests which can screen for Down's Syndrome?

Yes. There is a new test which can be undertaken in early pregnancy called CUB screening - Combined Ultrasound and Biochemical screening. It combines a blood test, maternal age, height and weight in addition to a measurement of the back of the babies neck. It can only be done between 11-14 weeks. The best time for the CUB Test is at 12 weeks. There is also a Triple Test which can be used to find out whether you are at higher risk of having a baby with Down's syndrome